<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>换皮肤</title>
    <style>
        .class1 {
            width: 100%;
            height: 400px;
            border: 5px solid red;
            font-weight: bolder;
            font-size: 20px;
            background-color: #FFD026;
        }

        .class2 {
            width: 100%;
            height: 400px;
            border: 10px solid red;
            font-weight: bolder;
            font-size: 50px;
            background-color: green;
        }
    </style>
</head>
<body>
<div id="div" class="class1">
</div>
<input type="button" value="皮肤1" ondblclick="theme('class1')">
<input type="button" value="皮肤2" ondblclick="theme('class2')">

</body>
</html>
<script>
    function theme(obj) {
        document.getElementById("div").className=obj;
    }
</script>